Purple Martins are migratory songbirds, the largest swallows in North America. They often form a unique relationship with humans, relying on human-provided housing for nesting. Each year, as winter approaches, these birds vanish from their North American breeding grounds, embarking on an extraordinary journey south.
Their Long Migration South
Purple Martins travel thousands of miles to their wintering grounds in South America. The vast majority spend their non-breeding season primarily in the Amazon Basin, including Brazil, Bolivia, and parts of Peru. Some populations also winter in Colombia, Venezuela, Ecuador, Paraguay, Argentina, British Guyana, Suriname, and French Guiana.
This journey can take weeks or months, with birds potentially covering up to 350 miles per day. Southward migration typically begins in late summer, from July to October depending on latitude. While some migratory species travel in large flocks, Purple Martins often journey in more solitary or loose groups. They generally migrate over land through Mexico and Central America, though some may cross the Gulf of Mexico or island-hop across the Caribbean.
Winter Life in South America
In South America, Purple Martins find abundant resources and mild weather. They continue to feed on flying insects, their primary diet. Unlike their breeding season, they do not establish individual nesting territories.
Instead, Purple Martins form massive communal roosts, often consisting of thousands to hundreds of thousands of birds. These roosts can be found near water, in trees, or in urban settings like city parks. A notable roost on Comaru Island in the Rio Negro hosts hundreds of thousands of martins between February and April, serving as a staging area before their return migration. While there, they also undergo their annual molt, replacing damaged feathers and ridding themselves of parasites.
The Reasons Behind Their Journey
Purple Martin migration is driven by two main factors: insect food sources and favorable climate conditions. Purple Martins are aerial insectivores, feeding exclusively on flying insects. In North America, the colder winter months lead to a drastic reduction in the population of flying insects, making it impossible for Purple Martins to find enough food to survive.
Tropical regions of South America, however, offer a consistent and abundant supply of flying insects throughout the northern winter. Their survival depends on this access to a reliable food source. Prolonged periods of cold temperatures or consistent rain, even in North America, can lead to starvation for martins due to the scarcity of insects. Their journey ensures access to a suitable diet and climate until the next breeding season.
Welcoming Them Back
Purple Martins begin their return migration to North America in late December or early January, with older birds typically arriving first. Their arrival dates in North America vary by latitude, with birds reaching the southern United States as early as January and northern regions in April or May.
The first martins to arrive, often referred to as “scouts,” are usually adult birds returning to their previous nesting sites. For those interested in supporting Purple Martins, preparing their housing is an important step. This involves cleaning and maintaining martin houses or gourds, ensuring they are ready for the birds’ return.
It is generally recommended to keep housing entrances closed until the first scouts are sighted in the area to deter other cavity-nesting birds from claiming the sites. Purple Martins exhibit site fidelity, meaning they often return to the same nesting location if their previous breeding season was successful.